Research has found airlines are charging customers up to £20 more to book over the telephone.
An investigation by Which? Travel found four of the UK’s five most popular airlines charge a higher fare to customer who book by phone.
It said the worst culprits are Ryanair and TUI, charging their customers an extral £20.
Easyjet also slapped on £15 while British Airways increased fares by £10.
Jet2, a Which? Recommended Provider, was the only airline in the investigation that did not charge its customers extra for booking via the phone.
Rory Boland, Which? Travel editor, said: "Not all customers are comfortable booking online, and they should not be penalised for booking over the phone.
"Airlines that are charging customers more must be clear and transparent about these additional fees."
Responding to the research, BA and TUI both argued that phone bookings add an additional admin cost.
Easyjet said: "We encourage passengers to book online. Those using our telephone service are informed of the online discount at the beginning of the call."
It said passengers needing special assistance would still get the online price when booking by phone.
Ryanair said: "Less than 0.5% of our customers choose to book over the phone."
